This invention relates generally to telephone systems and is particularly directed to the routing of subscriber initiated access code calls in accordance with the subscribing caller""s directory number.
Special access codes are used in telephone systems to facilitate access to commonly used services. These access codes consist typically of three digits such as 411 for directory assistance, 222 for voice mail service, 911 for emergency services etc. Because most telephone systems serve a large number of subscribers who are spread over a large geographic area, it is frequently necessary to route the access code call of a given subscriber to a particular source of the desired service. Thus, where two subscribers share a common telecommunications switching network, the call of a first subscriber living in a first community will be directed to a first service provider, e.g., a police or fire station, in the first community, while a call for the same service from a second subscriber in a second community will be routed to the corresponding service provider in the second community. There are currently several approaches for routing access code calls in accordance with individual subscriber information.
In Global System for Mobile Phones (GSM) wireless systems, two schemes known as xe2x80x9cCalling Party Categories (CPC) based routingxe2x80x9d and xe2x80x9cMSISDN/IMSI based routingxe2x80x9d are used to differentiate subscribers and achieve similar results. In this approach, the entire subscriber base is divided into a series of groups, with each subscriber group referencing a respective table in a digit analysis portion of a computer controlled telecommunications switch. For each service, such as fire or directory assistance, the routing scheme is fixed, i.e., all subscribers in a given group are routed in the same manner. For example, once the network administrator determines that all 979-xxxx subscribers are to be routed in a given way for xe2x80x9cfire service,xe2x80x9d then for any other service such as xe2x80x9chospital,xe2x80x9d the same 979-xxxx subscribers are routed in the same way. This limits the flexibility of the network administrator in terms of routing subscribers as the network administrator may want to route some subscribers with the 979 prefix in a different manner. In addition, the number of groups in which the subscribers can be classified is generally limited to 126 which further limits call routing flexibility.
Moreover, to accommodate special routing treatment covering different services, it is administratively difficult to create and manage various classes of subscribers, particularly when a new service is added to the network. For example, if there are five fire stations and six hospitals in the network, a total of 30 groups of subscribers would have to be created, such as group one for fire station-1 and hospital-1, group two designating fire station-5 and hospital-3, etc. Once these classes of services are assigned, adding a new service such as for xe2x80x9cpoison control,xe2x80x9d with five different poison control centers would require designing additional subscriber groups, possibly as many as 150 (30xc3x975), and redefining of the entire subscriber base. This would also require redefining the digit analysis tables within the telecommunications switch, which again typically is limited to 126 groups.
The problem of differentiating between subscribers can be solved by means of an Intelligent Network (IN). But IN networks are costly and require the transmission of information between the telecommunications switch and an external IN platform.
This invention is intended for use in a telephone network and contemplates the routing of designated access code telephone calls in accordance with the calling subscriber""s directory number (DN). In the telephone network, various services are available to the subscribers by dialing a three digit access code. These services include, but are not limited to, directory assistance (access code 411), police service (911), fire service (611) and voice mail service (222). When an access code is selected by a subscriber for accessing a desired service, a multi-digit translated number is generated corresponding to the three digit access code. The translated number is generated by a switch within the telephone network for proper routing of the call. In some situations, it may be desirable to route a call from one subscriber in a first area to a first service provider and a call from a second subscriber in a second area to a second, different service provider. This invention provides for the selective routing of access code calls on an individual subscriber basis using all or part of the subscriber""s DN. Thus, in the present invention all or part of the subscriber""s DN is added either to the beginning of the translated number as a prefix or to the end of the translated number as a suffix, or to both the beginning and end of the translated number, to provide a re-constructed number. The re-constructed number thus includes all or part of the subscriber""s DN and permits common access codes to be used by subscribers throughout the telephone network, while routing some subscriber calls differently from others where the same dialed digits are used. This invention may also be used without first entering a predetermined access code by adding all or part of the caller""s DN to the number dialed either as a prefix or suffix for the selective routing of calls based upon the caller""s DN. Thus, the calls to a given number from virtually any number of callers may be routed on an individual caller basis.